I think part of the problem is that the stem covers up what else should be in focus. But I don't think it's wrong, I agree, it adds an artistic element. The focus might have been easier to take if it was at the junction of the cap and stem, that way the stem would have led you to the cap. But I wouldn't change it, I like it.
The focus ended upon the rear of the mushroom. Did you do that manually or was it autofocus? I think if you pulled part of the stalk and more of the front of the image into focus it would be more appealing.
I like this very much. The focus disturbes a little bit but if you have done it intentionally it's a great idea. Also don't worry about the c-index. In my opinion, this kind of art is usually underrated.